This invention relates to collectorless direct-current motors, with a rotor, a detector for the rotor position, a motor winding arrangement which is supplied with current via a bridge circuit controlled by semiconductor switches acting dependent upon the rotor's angular position, and furthermore having a device for reducing the current in the bridge circuit during the time interval within which commutation of the motor winding arrangement is to occur.
Such motors are known from the German Pat. No. 1208 803 and from the published German allowed patent application ("Auslegeschrift") No. 25 085 46. To avoid, with the known motors short circuits during the stator current commutation, which would bring about an impermissible loading of the semiconductor switches and the source of the direct voltage, the bridge circuit of such motor is provided with a semiconductor switch connected in series with the bridge circuit (German "Auslegeschrift" 25 085 46), or else is provided with two such series-connected semiconductor switches (German Pat. No. 1208 803), these operating to block the current flow through the bridge circuit each time that commutation is to occur. This known device is effective and prevents short circuits and the resulting damage. It is, however, expensive since, in addition to the required, associated control devices, further heavy-duty, and thus expensive, semiconductor switches are required to block the total current to the bridge circuit.